Since “Kola superdeep borehole” is one of the most common search enquiries that take visitors to my site I’m adding a little note on that location..
In the 70s Russia and the States were not only seeing who will send more rockets to the outer space but also who will drill deeper into the Earth’s crust. Soviets won by going 1/3 of the way through the Baltic shielf with their 7 mile borehole 6 miles west from Zapolarny, which, in turn, is around 100 miles west from Murmansk.
From what I understand Zapolarny and area is no longer part of the “off limit to foreign travellers” zone starting Dec. 11 2008. But a lot of the surrounding territory is so I recommend you plan ahead and still arrange for permits.
Here is a film, in English, about this place: